使用mysql递归调用的存储过程 [英] Stored procedure with recursive call using mysql

问题描述

在此处输入图像描述 从二进制文件中获取优势

我尝试将存储过程与递归调用一起使用.我需要根据基于leg1的emp_name显示相关名称

I have tried using stored procedure with recursive call. i need to display relevant name based on emp_name based on leg1

但是它显示错误，例如#1414-例程sample.OUTVolume或INOUT参数2.在触发之前，getVolume不是变量或NEW伪变量

but it showing error like #1414 - OUT or INOUT argument 2 for routine sample.getVolume is not a variable or NEW pseudo-variable in BEFORE trigger

这是我的代码，

DELIMITER $$
CREATE PROCEDURE getVolume( IN param_name VARCHAR(255), OUT result VARCHAR(255 ))
BEGIN 
SELECT val INTO result FROM employee WHERE emp_name = param_name ;
IF result IS NULL THEN
select result;
ELSE     
CALL getVolume(result, '');
END IF;
END $$
DELIMITER ;



SET @@GLOBAL.max_sp_recursion_depth = 255;
SET @@session.max_sp_recursion_depth = 255; 
call getVolume('new', @result);
select @result;

推荐答案

@Shadow的答案正确.这是一个可以帮助您的实际示例:

The answer of @Shadow is correct. Here a practical example that can help you:

DELIMITER //

DROP TABLE IF EXISTS `employee`//
DROP PROCEDURE IF EXISTS `getVolume`//

CREATE TABLE `employee` (
  `emp_name` VARCHAR(255),
  `val` VARCHAR(255)
)//

INSERT INTO `employee` (`emp_name`, `val`)
VALUES
('demo', 'new'),
('new', 'd.new'),
('d.new', 'view'),
('view', 'hello'),
('hello', NULL)
//

CREATE PROCEDURE `getVolume`(
  IN `param_name` VARCHAR(255),
  OUT `result` VARCHAR(255)
)
BEGIN
  DECLARE `next_param_name` VARCHAR(255);
  SELECT `val` INTO `next_param_name`
  FROM `employee`
  WHERE `emp_name` = `param_name`;

  IF `next_param_name` IS NULL THEN
    SET `result` := `param_name`;
  ELSE
    -- CALL `getVolume`(`result`, '');
    CALL `getVolume`(`next_param_name`, `result`);
    -- SET `result` := CONCAT(`param_name`, ',', IFNULL(`result`, ''));
  END IF;
END//

DELIMITER ;

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